The background description provided herein is for the purpose of generally presenting the context of the disclosure. Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Natural response of the human eye to a change in ambient brightness includes adaptation of the eye pupil diameter through action of the iris, yielding a change in retinal illumination. For optical display systems having an exit pupil smaller than the actual eye pupil size, the mechanism provided by nature would no longer work as the retinal illumination is no longer dependent on the eye pupil diameter.